iOS NSURLSession的使用

1.NSURLSessionDataTask

    // 确定URL
    NSString *urlStr = @"http://localhost/试试看";
    urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *url = [NSURL URLWithString:urlStr];
    
    // 确定request
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:2.0f];
    
    // 确定会话
    NSURLSession *session = [NSURLSession sharedSession];
    
    // 由会话生成任务
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        NSLog(@"response-- %@",response);
        NSLog(@"data--%@",data);
        
        // 刷新UI,一定要返回主线程去刷新
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.imageView  setImage:[UIImage imageWithData:data]];
        });

    }];
    // URLSession默认生成的任务都是挂起状态,需要使用以下语句执行任务
    [dataTask resume];

2.NSURLSessionDownloadTask实现简单的下载功能

    // 确定URL
    NSString *urlStr = @"http://localhost/试试看";
    urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSURL *url = [NSURL URLWithString:urlStr];
    
    // 确定request
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:0 timeoutInterval:2.0f];
    
    // 确定会话
    NSURLSession *session = [NSURLSession sharedSession];
    
    // 由会话生成任务
    NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {
        // 从tmp中拷贝文件到cache
        NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
        NSURL *cachePathURL = [NSURL fileURLWithPath:cachePath];
        NSString *fileNameByMD5 = [[[response URL] absoluteString] MD5];
        NSURL *fileURL = [cachePathURL URLByAppendingPathComponent: fileNameByMD5];

        NSFileManager *mgr = [NSFileManager defaultManager];
        [mgr moveItemAtURL:location toURL:fileURL  error:NULL];
        
    }];
    
    [downloadTask resume];

- (NSString *)MD5
{
    const char *cStr = [self UTF8String];
    unsigned char digest[CC_MD5_DIGEST_LENGTH];

    CC_MD5(cStr, strlen(cStr), digest);

    NSMutableString *result = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];

    for(int i = 0; i < CC_MD5_DIGEST_LENGTH; i++) {
        [result appendFormat:@"%02x", digest[i]];
    }

    return result;
}

3.NSURLSessionDownloadTask实现复杂的下载功能:断点续传后台下载

http://blog.csdn.net/majiakun1/article/details/38133789